U.S. patent application number 10/505302 was filed with the patent office on 2005-10-06 for optical interconnect module, and ferrule comprising same.
Invention is credited to Flers, Alain, Rosinski, Bogdan, Yabre, Gnitaboure.
Application Number | 20050220404 10/505302 |
Document ID | / |
Family ID | 27636418 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050220404 |
Kind Code |
A1 |
Flers, Alain ; et
al. |
October 6, 2005 |
Optical interconnect module, and ferrule comprising same
Abstract
In order to make an optical interconnection of either two
optical fibers to each other or of one optical fiber with an
optoelectronic conversion circuit, it is planned to have a module
provided with a body or package in which sections of optical fibers
are overmolded. The overmolding on the one hand simplifies
industrial-scale manufacture and, on the other hand, enables the
adoption, for the optical fiber sections, of shapes such as flared
shapes and/or lenses enabling an appropriate refocusing or
collimation of the light rays conveyed by these optical fibers.
Inventors: |
Flers, Alain; (Bernard,
FR) ; Yabre, Gnitaboure; (Le Mans, FR) ;
Rosinski, Bogdan; (Brest, FR) |
Correspondence
Address: |
HARRINGTON & SMITH, LLP
4 RESEARCH DRIVE
SHELTON
CT
06484-6212
US
|
Family ID: |
27636418 |
Appl. No.: |
10/505302 |
Filed: |
May 9, 2005 |
PCT Filed: |
February 19, 2003 |
PCT NO: |
PCT/EP03/50023 |
Current U.S.
Class: |
385/33 |
Current CPC
Class: |
G02B 6/424 20130101;
G02B 6/4255 20130101; G02B 6/4267 20130101; G02B 6/4201 20130101;
G02B 6/4249 20130101; G02B 2006/12102 20130101; G02B 6/4232
20130101; G02B 6/421 20130101; G02B 6/1221 20130101; G02B
2006/12195 20130101 |
Class at
Publication: |
385/033 |
International
Class: |
G02B 006/32 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2002 |
FR |
0202249 |
Claims
1. Optical interconnection module comprising a package provided
with at least one optical section interposed between an input
optical port of the module and an output optical port of the
module, characterized in that the optical section is overmolded in
the package and forms an optical waveguide, in that the optical
fiber section comprises at least one flared cone getting enlarged
at one end of the section and forming an optical output section,
and in that the optical section comprises an end lens.
2. A module according to claim 1, characterized in that the lens is
formed by overmolding.
3. A module according to claim 1, characterized in that the package
is made of a material that has an optical refraction index lower
than an optical refraction index of an overmolded material forming
the optical section.
4. A module according to claim 1, characterized in that the lens is
made of a same material as that of the optical section.
5. A module according to claim 1, characterized in that the package
comprises a polymer material with efficient thermal behavior such
as, for example, an LCP, or a polyimide.
6. A module according to claim 1, characterized in that the package
is metallized.
7. A module according to claim 1, characterized in that the package
has a pedestal with gripping grooves.
8. A module according to claim 1, characterized in that the
overmolded optical section is curved to lead into a plane.
9. An optical ferrule comprising a module according to claim 1,
characterized in that the input optical port has a standardized
receptacle.
10. An optical ferrule comprising a module according to claim 1,
characterized in that it comprises an electronic integrated circuit
for the detection or emission of light rays, the integrated circuit
being mounted by reflow soldering of solder beads on the package.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] An object of the present invention is an optical
interconnection module and a ferrule comprising such a module, of
the type used in optical fiber transmission, especially but not
only to connect one end of an optical fiber to an electronic
circuit for the detection or emission of light rays.
[0003] An optical fiber is used essentially as a means to convey
information in the form of light signals that are normally
digitized. This means of transportation has the advantage of
efficiently resisting noise, especially electromagnetic noise, and
furthermore enabling very high data bit rates. However, since
processing in present-day computer devices is of the electronic
type, it is important to carry out an optoelectronic conversion of
the light signals to be processed at input and output of the
optical fiber. Furthermore, since the optical fibers may abut one
another, it is important to be able to connect them efficiently.
Various solutions have been devised to resolve these problems of
conversion and/or connection.
[0004] 2. Description of the Prior Art
[0005] Certain solutions have entailed the idea of making
harnesses. In these harnesses, an optical fiber or a bundle of
optical fibers is provided, fixedly at both ends (or at least at
one of its ends), with an optoelectronic conversion device. In this
case, the optical fiber delivers electrical signals or electronic
signals at one or both ends while it may deliver optical signals at
another end. The drawback of this type of solution is, firstly, the
cost generated by this integration of means. Secondly, the ease
with which the fiber can be handled is thereby greatly reduced.
Indeed, it will easily be understood that the length of the fiber
cannot be adjusted as easily as desired, especially if it is
provided on either side with electronic conversion circuits crimped
to the ends of the fibers. In this case, it is not at all possible
to lengthen or shorten the fiber. All that can be done is to
exchange it for another differently sized harness, which however
will also be a high-cost harness. Besides, the presence of the
electronic conversion circuit leads to the making of a joining
piece at the end of the optical fiber. The bulkiness of this
joining piece is inconvenient if the fiber has to be threaded into
narrow holes to conduct the signals from one place to another.
[0006] Furthermore, the mode of transmission in optical fibers may
depend on whether the nature of the fiber is single-mode or
multimode and/or on the device for the injection of light rays into
the fiber. Then, during the injection or extraction of the light
rays from an optical fiber, it is important to concentrate these
rays to the maximum extent on the core of the fiber whose diameter
is about 10 micrometers for a single-mode fiber (whereas it is
about 50 or 62.5 micrometers for multimode fibers). In practice,
there is then a loss in volume, with the light rays dispersing in a
wide-aperture cone, typically in the range of 20 degrees. The only
light rays used are those located in a solid angle beneath which, a
sensitive zone of an optoelectronic detector is perceived from the
core of an optical fiber or vice versa. This division in the solid
angle reduces the power injected or taken. Considerable losses are
thus encountered during the optoelectronic conversion, or even
during the connection of several optical fibers abutting one
another.
[0007] To resolve all these problems, there are known ways,
especially described in the document U.S. Pat. No. 5,168,537, for
placing focusing lenses in the path of the light rays so as to
concentrate their energy on the useful zone, namely the core of the
fiber or a sensitive zone of the detector. The positioning of these
focusing lenses is, however, the source of a drawback at the
industrial level because it necessitates operations to manipulate
microscopic objects for which, furthermore, the positioning must be
rigorously precise, given the tolerance values referred to here
above. Consequently, the devices presented in the above document
can be used only in the laboratory and not on a large-scale.
[0008] In the invention, to resolve the problem, it has been chosen
to manufacture one-piece ferrules by overmolding. In practice then,
the invention uses a package in which straight or curved grooves
are traced and then filled with an overmolding material. As the
case may be, the package is formed out of two half shells that are
assembled around the overmolding material. It will be shown that,
with this technique and with the shape of the grooves, it can be
chosen to form lenses more easily. The grooves will be V-grooves,
circular cylindrical, circular semi-cylindrical, or the like, and
their direction will be straight or curved. The lenses are obtained
either by the placing, at the ends of the ferrule, of an excess of
overmolding material that naturally adopts a lens shape with a
focusing power, or by making grooves whose transversal profile
develops especially in a cone shape at the ends of an optical guide
section thus made in the package. In this case, flared features are
made at low cost, providing for focal matching either at the
connection between two optical fibers or at the connection between
a transportation optical fiber and an optoelectronic conversion
circuit.
SUMMARY OF THE INVENTION
[0009] An object of the invention therefore is an optical
interconnection module comprising a package provided with at least
one optical section interposed between an input optical port of the
module and an output optical port of the module, characterized in
that the optical section is overmolded in the package and forms an
optical waveguide, in that the optical fiber section comprises at
least one flared cone getting enlarged at one end of the section
and forming an optical output section, and in that the optical
section comprises an end lens.
[0010] An object of the invention is also a ferrule provided with
such a module.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention will be understood more clearly from the
following description and the accompanying figures. These figures
are given purely by way of an indication and in no way restrict the
scope of the invention. Of these figures:
[0012] FIGS. 1a and 1b show longitudinal sectional views, along two
perpendicular planes, of the optical module of the invention;
[0013] FIG. 2 shows a sectional view of an example of an
integration of a module according to the invention in a complete
optoelectronic conversion ferrule and;
[0014] FIG. 3 is a sectional view showing an alternative embodiment
of the integration of FIG. 2.
MORE DETAILED DESCRIPTION
[0015] FIGS. 1a and 1b show an optical module 1 according to the
invention. This module 1 has a package 2 provided with at least one
optical section 3, comprising an optical fiber in one example, and
more generally light waveguides. The waveguide 3 is interposed
between an input optical port 4 and an output optical port 5 of the
module. In FIG. 1b, it can be seen that several optical section
such as 3 and 6 to 8 are active side by side, preferably in
parallel to one another, in the package 2. On the whole, the
package has a parallelepiped shape.
[0016] According to a main characteristic of the invention, the
package 2 is formed by a base made out of at least one first
material 9 (FIG. 1a) in which the waveguide sections 3 or 6 to 8
are overmolded. The waveguide sections are made of another
material. In practice the material 9 of the base could preferably
be a plastic material with an amorphous structure for example made
of a same material (COC or cyclic oleofin copolymer) as the
material constituting waveguide sections. At least the material 10
will be transparent to the light rays. Preferably, the material 9
will also be transparent to light rays and will possess a
refraction index, n2 smaller than a refraction index n1 of the
material 10 forming the waveguide. This mode of action ensures that
the overmolding operation is appropriate (the materials having same
mechanical properties), while at the same time ensuring the
waveguide character of the sections 3 or 6 to 8 made of the
material 10. As a variant, it can be planned that the material 9 of
the base will be a ceramic and that the material 10 of the
waveguides 3 or 6 to 8 will be molten glass.
[0017] The overmolding approach thus presented furthermore makes it
possible, using techniques of microsculpture, to impose a set of
particularly useful shapes for the waveguide 3, or for the sections
6 to 8. The micro-structuring techniques may be stamping or heat
embossing techniques, or else techniques of photolithography with
chemical etching or again techniques of laser etching. The aim is
to make grooves that are capable of receiving the overmolding
material 10. The overmolding material itself may be put in place by
micro-injection techniques, the conduit made in the material 9
possessing an inlet and an exit and thus being suitable for
injection.
[0018] As a variant, the package 2 made of material 9 may comprise
a body formed by a base 11 and a lid 12. The base and the lid may
both be made of a same material, for example a transparent material
with a refraction coefficient n2 lower than the coefficient of
refraction of the material 9 of the waveguide 3. However, the lid
12 could also be made with a gel having an appropriate refraction
index.
[0019] Within the framework of such a solution, preferably first of
all a pedestal 13 is made using a material capable of easily
accepting the material 9 of the base 11. For example, the material
of the pedestal 13, in the context of a plastic embodiment, will be
a PBT (polybutylene terephtalate), a polyimide, or a crystalline or
semicrystalline polymer possessing good mechanical behavior such as
liquid-crystal polymers (LCP). These materials furthermore have the
advantage of standing up to processing at high temperatures, the
justification of which shall be seen further below. If necessary,
in this case, the lid 12 may itself be mounted in a cap 14 having a
same function and a same nature as the pedestal 13 with respect to
the base 11. In particular, the base 13 will be provided with
relief features such as 15, with sharp edges in the form of grooves
or pads, enabling the material 9 of the base 11 to grip this
pedestal 13 in an efficient and industrially lasting way. The same
action will be taken, if necessary, for the lid 13 with respect to
the cap 14.
[0020] The base 11 is thus overmolded on the pedestal 13. After
this preferred overmolding, the base 11 is polymerized and then
sculpted, by etching or otherwise, in order to make conduits
therein, especially in the form of grooves designed to subsequently
serve as light waveguides. These sculpted conduits are then filled
in turn with an overmolding material 10 designed to form light
waveguides 3. Then the lid 12 is put into place and the material 10
is polymerized so as to be made rigid. If necessary, the
polymerization is done prior to the positioning of the lid 12, it
being possible to true the surface of the unit thus made before the
positioning of the lid 12. In this case, the lid itself is not
necessarily provided with grooves.
[0021] According to a particularly promising improvement of the
invention, the optical fiber sections 3 are provided, preferably in
the input port 4 and in the output port 5, but at least in one of
them, with flared cones such as 16 and 17 respectively. They are
even preferably surmounted with lenses such as 18 and 19. It is
furthermore possible to make the sections without flared portions,
but with lenses just as it is possible to make the sections with
flared portions but without the lenses. The flared portions have an
effect of improving the optical transfer. The lenses 18 and 19 have
a focusing or collimation effect that shall be explained further
below. Preferably, the lenses are obtained by the positioning of an
overmolding mold 20 when the waveguides are overmolded 3.
[0022] Preferably, the lenses are thus made of a same material as
the material 10 of the waveguides 3, and at the same time as these
waveguides 3. The flared portions 16 and 17 are such that the
waveguide section 3, made of optical fiber, has a smaller diameter
or a smaller section on the length of the package than the diameter
or section at the entry to the input port 4 or at the exit from the
output port 5. The shape of the section of the waveguide in the
longitudinal part may be circular or polygonal, preferably square
or rectangular in this case. The length of each of the flared
portions 16 and 17 is about one-tenth of the length of the sections
3.
[0023] FIG. 2 shows that the package 2 is more complete, especially
that the input port 4 has a receptacle 21 to receive a standardized
joining piece 22 mounted on a bundle 23 of optical fibers 24 to 27.
It forms a ferrule provided with the module of the FIGS. 1a and 1b.
The number of optical fibers in the bundle 23 is of course
preferably the same as that of the optical fiber sections in the
ferrule. According to the invention, each of the emitting or
receiving ends such as 28 of the optical fibers of the bundle 23
then respectively perceives a field 29 formed by a lens input face
such as 18. This field 29 is greater than these ends 28. As a
consequence, the energy transferred to or from the fiber section 3
is far more efficient.
[0024] At the other end, the package 2 of the ferrule 1 comprises
the output port 5 also provided with lenses 19. These lenses are
placed here so as to be facing integrated circuits 30 for the
detection or emission of light rays. These integrated circuits 30,
which are individualized and are equal in number to the number of
sections 3, are themselves placed on a driving integrated circuit
31.
[0025] According to one characteristic of this assembly, the
integrated circuits 30 are placed in a very rigorously precise way
on the driving circuit 31 through mounting by reflow soldering of
solder beads: surface tensions appear in these solder beads at the
time of the soldering and enable the perfect positioning (with a
tolerance of less than one micrometer) of these integrated circuits
30 at chosen places in this integrated circuit 31. The driving
circuit 31 is itself mounted on the package 2 by reflow of
soldering beads 32 enable a precise positioning of the connection
zones 33 of the circuit 31 relative to metallised zones 34 formed
on the package 2. In particular, the pedestal 13 or the cap 14,
which are made of materials that withstand very high temperatures,
enable these reflow operations. Thus a result is obtained wherein
the ferrule 1 provides a low-cost optoelectronic connection between
the circuits 30 and 31 and the bundle 23 of optical fibers.
[0026] Electronic tracks enable the electrical connection of the
circuits 31 and the circuits 30 to a main printed circuit, by means
of solder beads 32, comprising pads such as 35 (FIG. 3) located
beneath one face of the package, especially beneath the lower face
of the pedestal 13.
[0027] FIG. 3 shows an alternative embodiment of the ferrule of
FIG. 2. In FIG. 3, the pedestal 13 has a right end foot 36 opposite
the input port 4. This foot 36 is of great height and rises towards
a lid (not shown) of the ferrule. FIG. 3 is presented along the
plane perpendicular to the plane of FIG. 2. In this FIG. 3, the
bundle 23 is seen along the edge. The sections 3 therein have the
particular feature of having an elbow 37 by which it is possible to
ensure that the output port 5 is not in a rectilinear alignment
with the input port 4 along the section 3.
[0028] Such an elbow 37 fulfils the same role as the mirror of the
prior art 24 referred to, but at lower cost. With such an elbow 37,
the circuit 30, and the circuit 31 can again be in a plane of the
printed circuit (not shown) that bears the ferrule 1 (or in a
parallel plane). In the first case, which is not shown, the elbow
37 will be oriented toward the plane of the pads 35. The pedestal
13 could be filled at the position of the pads to let out the
material 9 of the base 11 and the material 10 of the guide 3.
[0029] In the case of these elbows 37, the embodiment using
overmolding may comprise the making of several vertical slices in
which grooves are made, having an end in the shape of a cross-head
(the end may or may not be provided, at the end of the cross-head
with a flared portion 17). The different slices are then attached
to one another and the material that has to constitute the sections
3 is injected into the galleries thus formed by the joining of
slices against one another. As a variant, the slices are provided
with a grooves on only one side, and these grooves are filled when
flat by overmolding of the material 10. Then the slices are
assembled against one another, after truing if necessary. This
embodiment then makes it possible to present the integrated circuit
31 (provided with its emitting or detecting integrated circuits 30)
parallel to a plane of a general printed circuit on which the
ferrule 1 is positioned. To this end, metallised connections 38
coming from the metallizations 34 made in the package 2 run along
the right foot 36, up to the pads 35. The metallizations of the
pads 35 enable the electrical connection of the circuit 31 with a
reception printed circuit as well as the holding of the ferrule 1,
by soldering, to this reception printed circuit.
[0030] It would furthermore be possible to form the lenses 18 or 19
out of a material with a refraction index that is different from
that of the material used to form the sections 3 and the flared
portions 16 and 17. However, preferably, a same material will be
used, for reasons of simplification of manufacture.
* * * * *